Process to upgrade oil using metal oxides

ABSTRACT

Described herein are compositions and methods for using metal oxides to upgrade oil. Metal oxides may be used as catalysts to reduce the TAN of the oil by converting carboxylic acids such as naphthenic acids into non-corrosive products. In some cases, the conversion occurs by a decarboxylation of the carboxylic acid to produce CO 2 . A second process promoted by metal oxides is hydrocarbon cracking. Cracking decreases the viscosity and increases the API, and produces lower molecular-weight hydrocarbons that are useful for many fuels and lubricants. Reductions in TAN and the increases in API improve the quality of increase the value of oil.

This application claims the benefit of priority from U.S. ProvisionalApplication Ser. No. 60/586,026, filed Jul. 7, 2004.

GOVERNMENT RIGHTS

The United States Government has certain rights in this inventionpursuant to Grant No. DE-FC26-02NT15383; S-105,724 awarded by the U.S.Department of Energy.

FIELD OF THE INVENTION

The invention relates to methods useful for upgrading, or improving thequality of oil.

BACKGROUND OF THE INVENTION

Crude oil, or petroleum, is a complex mixture of hydrocarbons that isthe basis for the world's energy economy. Crude oil, which is usuallyhighly viscous, often contains contaminants, including water, suspendedsolids, water-soluble salts, and organic acids. These contaminantscorrode pipes and oil processing equipment, leading to reduced oilquality.

Naphthenic acids, a collection of unfunctionalized aliphatic, alicylic,and aromatic carboxylic acids, are found to varying degrees in crudeoil, and are especially prevalent in heavy or biodegraded oils.Naphthenic acids have a high degree of chemical reactivity, and inaddition to being recognized as a major source of corrosion intransportation pipelines and distillation units in refineries, theyoften react with other materials to form sludge and gum that plugpipelines and operating machinery. As a result, oil products with highconcentrations of naphthenic acid are identified as being of poorquality and result in a lower price in the market.

Due to its complex compositional heterogeneity, it is presently verydifficult to predict the severity of the corrosion of an individual or asmall group of NA compounds by any analytic measurements. A TotalAcidity Number (TAN) or the neutralization number (Neut Number), definedby the number of milligrams of KOH required to neutralize the acidity inone gram of oil, is therefore the commonly adopted criterion forpredicting the corrosive potential of a crude oil. With this standard,high TAN oils (>0.5 mg KOH/g) are less desirable than lower TAN oils,resulting in a much lower price. Crude oils from California, Venezuela,North Sea, Western Africa, India, China and Russia have typically highernaphthenic acid contents. The development of a naphthenic acid removalprocess will significantly help the petroleum industry in improvingrefinery processing of heavy crude oils possessing high contents ofnaphthenic acid.

Another important component in the process of refining crude oil is theprocess of converting crude oil into smaller hydrocarbon components thatare useful for lighter fuels and lubricants. This process is known as“cracking,” and involves the cleavage of carbon-carbon bonds, resultingin hydrocarbons with lower boiling points. There is an ongoing need inthe art for lower-temperature methods that lead to the reduction in oilviscosity.

The conventional method to remove naphthenic acid is based on a causticwash to neutralize the organic acids present in crude oil. However, thistreatment results in the formation of an emulsion that, once formed, isdifficult to break down or remove. Furthermore, the salts of many largernaphthenic acids remain in the oil after neutralization. An alternativeapproach is to mix oil containing high levels of naphthenic acid withoil(s) having a low level of naphthenic acid, thereby diluting thenaphthenic acid. While this approach does ultimately reduce theconcentration of carboxylic acid in the oil sample, it does noteffectively remove naphthenic acids.

Several U.S. patents relate to the process of upgrading oil. Forexample, U.S. Pat. No. 5,985,137 describes the use of alkaline earthmetal oxides as catalysts to reduce the TAN of oil. U.S. Pat. No.6,547,957 describes a method for decreasing the TAN and increasing theAPI gravity using non-metal oxide catalysts. U.S. Pat. Nos. 6,096,196and 5,961,821 describe methods for removing naphthenic acids usingalkoxylated amines. However, the techniques described in theaforementioned references, each of which is incorporated by referenceherein, are limited in their commercial application or leave room forsignificant improvement.

Based on the ongoing demand for refined petroleum, there is asignificant need in the art for improved techniques to both reduce theviscosity of oil, as well as reduce the amount of naphthenic acids inoil.

SUMMARY OF THE INVENTION

The invention described herein provides compositions and methods forupgrading oil using metal oxides. One embodiment of the inventioncomprises a method for upgrading oil, in which a quantity of an oil iscontacted with an amount of a metal oxide agent sufficient to upgradethe quantity of oil.

Further embodiments include methods wherein the metal oxide agent isselected from the group consisting of alkaline earth metal oxides,oxidative transition metal oxides, rare earth metal oxides, andcombinations thereof.

Additional embodiments include methods wherein the alkaline earth metaloxide is selected from the group consisting of calcium oxide (CaO),magnesium oxide (MgO), as well as oxides of beryllium (Be), oxides ofmagnesium (Mg), oxides of calcium (Ca), oxides of strontium (Sr), oxidesof barium (Ba) oxides of silver (Ag), oxides of copper (Cu), oxides ofmanganese (Mn), oxides of lead (Pb), oxides of nickel (Ni), oxides ofcerium (Ce), oxides of lanthanum (La), oxides of yttrium (Y), oxides ofzirconium (Zr), and combinations thereof.

Still further embodiments include methods wherein the oxidativetransition metal oxide is selected from the group consisting of AgO,Ag₂O, and combinations thereof.

Other embodiments of the invention relate to the temperature of thereaction, wherein the above-described contacting step is performedwithin a temperature range selected from the group consisting of fromabout 200° C. to about 450° C., from about 250° C. to about 450° C.,from about 300° C. to about 450° C., from about 350° C. to about 450°C., and from about 400° C. to about 450° C., as well as from about 300°C. to about 370° C.

Other embodiments include oil upgrading systems wherein theabove-described contacting is carried out in a reaction system selectedfrom the group consisting of a sealed glass tube, an autoclave, a flowreactor, a batch reactor, a slurry reactor, and combinations thereof.

Further embodiments include methods wherein the quantity of oil islocated in a subsurface reservoir.

Further embodiments include methods wherein the oil is a fat-based oil.

Further embodiments include methods wherein water is added to dissolvewater-soluble impurities.

Further embodiments include methods wherein pyridine, nickel (Ni),copper (Cu), and/or Al₂O₃ are added to promote acid conversion.

Further embodiments include methods in which the quantity of oil iscontacted with an amount of an adsorbent material sufficient to reducethe total acidity of the quantity of oil.

Still further embodiments include methods wherein the adsorbent materialis a clay mineral or a mixture of clay minerals. These minerals may beselected from the group consisting of kaolinite, illite,illite-smectite, palygorskite, montmorillonite, Ca-montmorillonite,sepiolite, hectorite, Na-montmorillonite, and combinations thereof.Contacting the quantity of oil with the adsorbent material and with themetal oxide agent may occur in parallel, in series, or simultaneously.Other embodiments include methods wherein the adsorbent materialcatalyzes acid conversion.

Another embodiment involves a method for reducing the total acidity of aquantity of oil, comprising contacting the quantity of oil with anamount of a metal oxide agent sufficient to reduce the total acidityand/or the total acid number of the quantity of oil.

An additional embodiment includes a method wherein reducing the totalacidity comprises reducing a quantity of naphthenic acids in thequantity of oil.

Further embodiments include methods for reducing the viscosity of aquantity of oil, comprising contacting the quantity of oil with anamount of a metal oxide agent sufficient to reduce the viscosity of thequantity of oil. Additional embodiments include methods wherein reducingthe viscosity of the quantity of oil comprises increasing the APIgravity of the quantity of oil.

Further embodiments include compositions comprising a quantity of anupgraded oil, produced by a process, comprising: providing a quantity ofan oil; and contacting the quantity of oil with an amount of a metaloxide agent sufficient to upgrade the quantity of oil.

Still further embodiments include compositions of upgraded oil whereinthe metal oxide agent used in its production is selected from the groupconsisting of alkaline earth metal oxides, oxidative transition metaloxides, rare earth metal oxides, and combinations thereof.

Additional embodiments also include compositions of upgraded oil whereinthe process further comprises contacting the quantity of oil or thequantity of upgraded oil with an amount of an adsorbent materialsufficient to reduce the total acidity of the quantity of oil or thequantity of upgraded oil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a process of acid conversion, in accordance with anembodiment of the present invention.

FIG. 2 illustrates the type of reaction that may occur during metaloxide-mediated acid conversion, in accordance with an embodiment of thepresent invention. Magnesium oxide is shown for purposes ofillustration.

FIG. 3A shows two of the methods for removing carboxylic acids inoil—adsorption and catalytic treatment—in a series, in accordance withan embodiment of the present invention.

FIG. 3B shows two of the methods for removing carboxylic acids inoil—adsorption and catalytic treatment—in parallel, in accordance withan embodiment of the present invention.

FIG. 4A shows the reaction setup for a fixed-bed flow reactor, inaccordance with an embodiment of the present invention. P₁ and P₂ arepressure gauges to indicate the system pressure changes upstream anddownstream of the reaction. TC represents a temperature control unit.

FIG. 4B shows a fixed-bed catalyst portion of a flow reactor, inaccordance with an embodiment of the present invention.

FIG. 5A shows a titration curve of potassium acid phthalate toKOH/isopropanol solution, in accordance with an embodiment of thepresent invention.

FIG. 5B shows a titration curve of KOH/isopropanol solution to oilsample, in accordance with an embodiment of the present invention.

FIG. 6 shows a MgO-catalyzed decarboxylation reaction, (a) TemperatureEffects, and (b) Catalyst-Loading Effects, in accordance with anembodiment of the present invention.

FIG. 7 shows a concerted MgO-catalyzed decarboxylation pathway, inaccordance with an embodiment of the present invention.

FIG. 8 shows an acid conversion of an oil sample using various metaloxide catalysts, in accordance with an embodiment of the presentinvention.

FIG. 9 shows the thermal treatment of crude oil, in accordance with anembodiment of the present invention.

FIG. 10 shows a flow reaction in the presence of MgO below 250° C., inaccordance with an embodiment of the present invention.

FIG. 11 shows a flow reaction in the presence of MgO at 300° C. and 350°C., in accordance with an embodiment of the present invention.

FIG. 12 shows a flow reaction in the presence of MnO₂ at 250° C., inaccordance with an embodiment of the present invention.

FIG. 13 shows a correlation between NA adsorption with the percentage ofMgO in clay, in accordance with an embodiment of the present invention.

FIG. 14 shows the TAN over time at 300° C. in a reaction containingcrude oil and MgO, in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The aims of the instant application are to provide cost-effectivemethods for upgrading and/or improving the quality of oil using metaloxides. In accordance with alternate embodiments of the presentinvention, two methods that may be implemented separately or together toachieve this are: (1) to reduce the amount of carboxylic acids, such asnaphthenic acids, present in the oil, and (2) to decrease the viscosityof the oil. The present invention is based on surprising studies thatdemonstrated that metal oxides can be used to upgrade oil. Otherfeatures may be added to the process, as described in greater detail inthe ensuing discussion. Treatment of oil with the metal oxides disclosedherein may improve the quality of oil by both decreasing carboxylic acidlevels and by decreasing the viscosity of the oil.

Unless defined otherwise, technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. One skilled in the art willrecognize many methods and materials similar or equivalent to thosedescribed herein, which could be used in the practice of the presentinvention. Indeed, the present invention is in no way limited to themethods and materials described.

As used herein, the term “oil” refers to a liquid, hydrocarbon orfat-based substance that is derived from animals, plants, mineraldeposits, or is manufactured artificially. Oils are generally notmiscible with water. The term “oil” also encompasses petroleum andpetroleum derivatives.

As used herein, the term “petroleum,” or crude oil, refers to anaturally occurring mixture composed predominantly of hydrocarbons inthe gaseous, liquid or solid phase. Petroleum can be processed (refined)into a number of useful products including asphalt, diesel fuel, fueloil, gasoline, jet fuel, lubricating oil, and plastics.

Two mechanisms to reduce the levels of carboxylic acids in oil include:(1) acid conversion, a process by which carboxylic acids are convertedinto non-corrosive components, and (2) the use of a solid adsorbent toremove carboxylic acids from the system. A goal of both of theseprocesses is to reduce the Total Acid Number (TAN) of the sample. Inconnection with various embodiments of the present invention, thesetechniques may be implemented together or separately.

The TAN, or neutralization number, is defined by the number ofmilligrams of KOH required to neutralize the acidity in one gram of oil.The TAN and the neutralization number are the commonly adopted criterionfor predicting the corrosive potential of crude oil. High TAN oils (>0.5mg KOH/g) are less desirable than lower TAN oils, resulting in a muchlower price when such oils are sold in the market. Crude oils fromCalifornia, Venezuela, North Sea, Western Africa, India, China andRussia typically have a higher TAN than crude oil obtained from othersources.

Another technique for improving the quality of oil is to decrease theviscosity of oil by converting large hydrocarbons into smaller ones.This process is also known as “cracking.” Viscosity is a measure of theresistance of a fluid to deformation under shear stress. It is commonlyperceived as “thickness,” or resistance to pouring. Viscosity describesa fluid's internal resistance to flow and may be thought of as a measureof fluid friction. A useful unit for quantitating viscosity is the“centipoise,” or cP. An alternate unit for viscosity that is often usedis “API gravity.”

The term “API gravity” refers to the commonly accepted scale adopted bythe American Petroleum Institute (API) for expressing the density ofliquid petroleum products. The API gravity is related to the specificgravity, which is the ratio of mass of any material to the mass of thesame volume of pure water at 4° C. Units of API gravity are expressed asdegrees, and in general, the higher the API gravity, the lighter the oiland the lower the viscosity. Crude oil is often classified as light,medium or heavy, according to its measured API gravity. Generallyspeaking, higher API gravity degree oil values have a greater commercialvalue and lower degree values have lower commercial value.

As used herein, the term “cracking” refers to a process by which complexsubstances, such as the high molecular weight hydrocarbons in petroleum,are broken down into smaller molecules (that tend to have lower boilingpoints). Cracking generally involves breaking carbon-carbon bonds.Cracking may occur as a result of a number of processes including heat(thermal cracking) and catalysis (catalytic cracking). Treatment of oilwith metal oxides may increase the quality of the oil by promoting thecracking process. Contacting oil with one or more metal oxides may allowthe cracking process to occur at lower temperatures.

As used herein, the term “upgrade” refers to a process in which thequality of an oil is improved. Upgraded oil may be defined as oil thathas undergone a process resulting in a substantial decrease in its totalacidity, a substantial increase in its viscosity, or a combinationthereof. A “substantial” decrease in the total acidity, as that term isused herein to modify total acidity, may be defined as a decrease in theTAN that is greater than one TAN unit. A “substantial” decrease in theviscosity, as that term is used herein to modify viscosity, may bedefined as an increase in the API gravity that is greater than one APIdegree, or a decrease in the cP number by greater than one cP.

A process of upgrading oil is illustrated in FIG. 1. In FIG. 1, crudeoil or feed 101 is pumped into the system by an oil pump 102. Theprocess may include a flow control system 103. A unit 104 may also beincluded in which pre-heating of the oil and adsorbtion of naphthenicacids may be performed. Box 105 indicates an optional water or gas purgestep. The process may also include a catalytic converter 106; the unitof the apparatus that may contain the metal oxide catalyst and where theoil-upgrading reactions occur. Following catalysis, the oil may passthrough a cooling unit 107. A temperature and pressure control unit 108for the catalytic converter 106 may also be included. Box 109 representsthe product of catalytic conversion. Following a round of catalyticconversion, it may be desirable to repeat the process in order toupgrade the oil further. To accomplish this, Box 110 shows an optionalrecycling loop. The oil upgrade process often results in the productionof gases, which are designated by Box 111. These gases may be purified,as shown in Box 112, and then may be partially burned to generate heatfor the catalytic conversion as shown in Box 113. Oil that has undergonethe processing described above may then be sent to a refinery forfurther processing, as shown in Box 114. FIG. 1 is shown only as ageneral illustration of the process; one of skill in the art wouldrecognize that components process may be added, deleted, or modified tosuit individual needs.

Acid conversion is a process by which organic carboxylic acids such asnaphthenic acid are decarboxylated, often resulting in a decrease in theTAN. One possible product of acid conversion is carbon dioxide (CO₂).However, acid conversion may also occur in the absence of CO₂production. Other possible products of acid conversion include theformation of carboxylic acid salts through traditional acid-basereaction and/or the formation of alkaline earth metal carbonates throughthe adsorption of CO₂ by metal oxides. Examples of reactions that mayoccur during a metal oxide-mediated acid conversion are illustrated inFIG. 2, in which MgO is used for purposes of illustration.

An alternative method to acid conversion for decreasing the TAN involvesthe binding of carboxylic acids by an adsorbent solid material. Anadsorbent is a material that is capable of the binding or collectingsubstances or particles on its surface. As will be readily recognized bythose of skill in the art, a number of adsorbent materials may be usedto remove acids from oil and/or reduce the TAN, including, by way ofexample, a number of different clays. In one embodiment of the presentinvention, adsorption and catalytic acid conversion may be performedindividually, or in series, as shown in FIG. 3A, to reduce the TAN of aquantity of oil. When the adsorption and acid conversion occur inseries, a quantity of oil is subjected to one process and then the samequantity of oil is subjected to the other process. A series reaction maytake place with either the acid conversion or the adsorption occurringfirst.

In a further embodiment of the present invention, the acid conversionand the adsorption may be carried out in parallel, as shown in FIG. 3B.In those embodiments of the instant invention in which the reaction iscarried out in parallel, two different quantities of oil are treated;one is contacted with a metal oxide to promote acid conversion, and theother is contacted with an adsorbent to remove carboxylic acids.Following a parallel reaction, the two quantities of oil may becombined; although this is not required. 301 represents the area of thesystem where adsorption may take place in a series reaction. 302 showswhere catalytic treatment may occur in a series reaction. Boxes 303 and304 show where adsorption and catalytic treatment may occur in aparallel series, respectively.

In yet another embodiment of the present invention, adsorption and acidconversion occur simultaneously with a quantity of oil. Indeed, as willbe readily recognized by those of skill in the art, a single materialmay be used to perform both adsorption and acid conversionsimultaneously. For instance, a number of different metal-oxidecontaining clay minerals may be able to catalyze both the acidconversion and the adsorption.

Metal oxides are defined as compounds comprising one or more metal atomscombined with one or more oxygen molecules. Different classes of metaloxides include alkaline earth metal oxides, oxidative transition metaloxides, and rare earth metal oxides. Examples of alkaline earth metaloxides include, but are not limited to, oxides of calcium (Ca),strontium (Sr), magnesium (Mg), and barium (Ba). Examples of oxidativetransition metal oxides include, but are not limited to, oxides ofsilver (Ag), copper (Cu), manganese (Mn), lead (Pb), nickel (Ni), cobalt(Co), and iron (Fe). Examples of rare earth metal oxides include, butare not limited to, oxides of the lanthanide series, as well as cerium(Ce), lanthanum (La), yttrium (Y), and zirconium (Zr), and scandium(Sc). As will be readily recognized by those of skill in the art, thereare many metal oxides suitable for use in connection with alternateembodiments of the present invention.

The term “metal oxide agent,” as used herein, refers to a metal oxide ormixture of metal oxides. A metal oxide agent may also comprise otheradditional inert ingredients.

The term “contacting,” as used herein, refers to a process by which twoor more reaction components are placed in sufficiently close proximityto one another such that they are able to chemically react with oneother.

The term “naphthenic acids,” as used herein, refers to a group ofunfunctionalized aliphatic, alicylic, and aromatic carboxylic acids thatare often found in petroleum and petroleum products. Naphthoic acid is atype of naphthenic acid that generally has the formula C_(n)H_(2n).

One of skill in the art will recognize that there are a variety ofdifferent types of reactors that would be suitable for the process ofupgrading oil in connection with alternate embodiments of the instantinvention. Several examples are provided here, but the application ofthe instant invention is not in any way limited to the use of theseparticular reactors. One system for carrying out an acid conversionreaction is a sealed glass tube batch reactor. An acid sample, catalyst,and/or other additive (if any), in milligram quantities, may be sealedin a glass tube under a vacuum. The sealed glass tubes may then beplaced in oven to start a desired reaction under controlled reactionconditions. The reactions may be carried out at the temperature range offrom about 200° C. to about 450° C. for about 4 hours, althoughtemperatures outside this range as well as longer or shorter incubationtimes may also be suitable; particularly depending upon theconfiguration of the system and its scale. The reaction gas may becollected and quantified in a vacuum line using a standard gas transfermethod.

For crude oil test experiments, larger sample volumes are often needed,and an alternative experimental procedure that uses an autoclave reactorhas been established. For example, an autoclave reactor with the volumeof approximately 40 mL may used. A sample operation procedure is asfollows: (i) a quantity of an oil and a metal oxide agent (2˜5 wt % ofoil) are added to the reactor; (ii) the components are mixed by shakingthe reactor for one hour; (iii) the reaction is incubated at atemperature range of 250-300° C. for 4 hours while keeping the reactormoving to maintain contact between the reactants and catalysts; (iv) thereactor is cooled at the end of the reaction and the treated oil isrecovered by solvent extraction using dichloromethane or anothersuitable solvent. The solvent extraction may be carried out, forexample, by vacuum filtration and followed by evaporation of thesolvent.

As illustratively depicted in FIG. 4A, an alternate system for carryingout the acid conversion includes a flow reactor system, which generallyhas a low operating cost. A flow reactor may have either a fixed-bedcatalyst or a non-fixed-bed catalyst. In a flow reactor, the reactantfluid flows through one or more tubular reactors containing the catalyst(See FIG. 4B). Flow reactors may operate continuously and often allowthe acid conversion to occur in one pass. Additionally, they allow arelatively long catalyst contact time, and provide a straightforwardprocess to separate the products from the catalyst.

In a flow reactor setup, a pump 400 is used to pump decane, or anothersuitable solvent, into a transfer vessel 402 at a constant flow rate.Pressure gauges 1 and 2 (401 and 403, respectively) indicate systempressure changes upstream and downstream of the transfer vessel. Crudeoil is added to the other side of the transfer vessel and is pressed outby the decane through a transfer piston. An N₂ (or other suitable gas)purge line 404 may be used to purge the oil from the system after thereaction. The catalysis takes place in a furnace 405, which is regulatedby a temperature control unit 406. The resulting oil may be collected ina vessel 407 at the end of the reaction. The reaction may have stopvalves (408 and 409, respectively). The transfer tubing lines and valvesmay be wrapped with heating tape and maintained at or about 80° C. tokeep the oil at a temperature where it flows easily; although thistemperature can be varied in connection with alternate embodiments ofthe present invention. Optional components of a flow reactor systeminclude, but are not limited to, flow control units, heat supplysources, oil recycling loops, oil cooling units, and the like, whichwill be readily recognized by those of skill in the art. A fixed-bedflow reactor system may be scaled up to accommodate reaction volumesrequired for industrial applications.

Other types of reaction systems that may be suitable for the acidconversion process include a batch reactor system and a slurry reactorsystem. A batch reactor is a system in which the reaction components areadded to a tank or other suitable container. In general, all reactioncomponents are added at the beginning of the reaction, and productsremain in the tank until the reaction has progressed for the desiredamount of time. Following the reaction, the products are removed foranalysis or further processing. A slurry reactor is similar to a batchreactor, except that the catalyst is continuously mixed with thereactants to maintain the reaction mixture as a slurry, which is definedas a liquid containing suspended solids. Both batch and slurry reactorsystems may be readily scaled up to accommodate the needs of anindustrial setting by persons having ordinary skill in the art.

Decarboxylization is significant in the acid conversion process.Theoretical studies of the decarboxylation mechanism suggest that theradical pathway will be predominant when transition metals such asCu(II) and Mn(III) are involved. These cation species are able togenerate an internal electron-transfer due to the closed-shell (fromCu(II), −3d⁹ to Cu(I), −3d¹⁰ electronic configurations) and halfclosed-shell (from Mn(III) −3d⁴ to Mn(II) −3d⁵ electronicconfigurations). These studies also suggest that the concerted pathwaysmay be a mechanism when involving base metals. In a concerted pathway, anucleophilic attack on the β-carbon is the initiative step. Thesestudies still further suggest that the hydroxyl group on the metalsurface may assist the breaking of the carbon-carbon bond. While notwishing to be bound by any particular theory, it is believed possiblethat basic conditions promote the initial base-acid reaction, whileacidic conditions promote the subsequent decarboxylation reaction.

In addition to acid conversion, adsorption is an effective method forremoving carboxylic acids, such as naphthenic acid, from oil. The“adsorbent material” refers to a material that has a capacity ortendency to adsorb another substance. Clay minerals have been used assolid absorbents to remove naphthenic acid. The major components of clayminerals are silica, alumina, and water, frequently with appreciablequantities of iron, alkali, and alkaline earth cations. Natural claysusually have high cation-exchange capacity (CEC) and surface areas. Inaddition, they are inexpensive and environmentally friendly. Clayminerals may interact with many organic compounds to form complexes ofvarying stabilities and properties. Clay organic interactions aremultivariable reactions involving the silicate layers, the inorganiccations, water and the organic molecules. The chemical affinity betweenthe acid compound and the solid surface depends on structure (molecularweight, chain length, etc.) of the acid molecule, functional groupspresent in the acid molecule such as hydrophobic groups (—C—C—C—C—),electronegative groups (—C═O, —C—O—C—, —OH), π bonds (—C═C—, aromaticrings), and configuration of the acid molecule (Kowalska, M. et al., TheSci. of the Total Environ., (1994) 141, 223-240). Examples of clays thatmay be useful for adsorbing metal oxides include but are not limited tokaolinite, illite, illite-smectite, palygorskite, montmorillonite,Ca-montmorillonite, sepiolite, hectorite, and Na-montmorillonite.

Zeolites may also be used to partially upgrade oil. Zeolites aresynthetic or naturally-occurring minerals that have a porous structure.In general, they are hydrated alumino-silicate minerals with an openstructure that can accommodate a variety of positive ions as well asother compounds. Some of the more common naturally-occurring mineralzeolites are: analcime, chabazite, heulandite, natrolite, phillipsite,and stilbite. An example mineral formula is: Na₂Al₂Si₃O₁₀-2H₂O, theformula for natrolite. Natural zeolites form where volcanic rocks andash layers react with alkaline groundwater. There are several types ofsynthetic zeolites that form by a process of slow crystallization of asilica-alumina gel in the presence of alkalis and organic templates.Zeolites in the ZSM and HZSM families may be coated with substances thatmay be useful for upgrading oil. ZSM-5 is already well known for itsutility in cracking oil.

The methods described above are useful for removing corrosive materialssuch as carboxylic acids from petroleum. However, this process is alsosuitable for other fat-based oils, such as plant and animal-derivedoils, as will be readily recognized by those in this, and related fieldsof art, and the application of the inventive technology to such relatedfields is considered to be within the ambit of the present invention.These other types of oil often contain naphthenic acids that lead tounwanted chemical reactions that negatively affect their stability.Therefore, methods of removing acids in these types of oils is a usefulgoal and lies within the scope of this invention.

Methods for upgrading the quality of oil are applicable both above thesurface of the earth, as well as below the surface, such as in anunderground oil reservoir. The reactors used in connection withalternate embodiments of the present invention may thus be configuredfor use in above-ground or underground settings. Either or both of theseconfigurations may be desirable depending upon the particular industrialapplication of the inventive technology.

In an alternate embodiment of the present invention, a range ofdifferent substances may be added to one or more of the oil upgradereactions described herein that aid in the reaction process or promoteor enhance the upgrade. Some such additives are water and pyridine,copper, nickel, Al₂O₃ and other metallic or organic substances.

An individual of ordinary skill in the art will recognize that theprocesses described herein may be carried out at a variety of differenttemperatures, for varying lengths of time, depending on the type ofreactor, sample size and a number of other conditions. Examples oftemperature ranges that may be suitable for contacting a sample of oilwith a metal oxide in connection with alternate embodiments of thepresent invention are as follows, although are in no way limited to:from about 200° C. to about 450° C., from about 250° C. to about 450°C., from about 300° C. to about 450° C., from about 350° C. to about450° C., from about 400° C. to about 450° C., and from about 300° C. toabout 370° C. These ranges are given by way of illustration and not byway of limitation.

The following examples are offered by way of illustration, and not byway of limitation.

EXAMPLE 1

Total Acid Number Measurement

An in-house Total Acid Number (TAN) measurement method was developedfollowing the procedure of ASTM standard method D664. The principle ofthis measurement is based on non-aqueous acid base potentiometrictitration determined by a PH/mv meter (Oakton PH510 Series).

Procedures

Preparation of Alcoholic Potassium Hydroxide Solution

6 g of KOH were added to approximately 1 L of anhydrous isopropanol. Thesolution was then gently boiled for 30 min to increase the solubility ofKOH in the solution. The solution was stored overnight and thenstandardized with potassium acid phthalate (KHC₈H₄O₄ or KHP).

Standardization of Alcoholic KOH Solution

The solution was standardized with potentiometric titration of weighedquantities of KHP dissolved in CO₂-free water.

Preparation of Oil Sample

One 5 g oil sample was dissolved in 125 mL titration solvent (500 mLtoluene/495 mL anhydrous isopropanol/5 mL water). The resulting solutionwas then filtered and transferred to a 250 mL beaker, which is used asthe titration vessel.

Titration of KOH to Oil Sample

A suitable amount of KOH alcoholic solution was added. Once a constantpotential has been observed, the meter readings were recorded. When thesample has been titrated close to the inflection point, fewer drops ofKOH were added. For each set of samples, a parallel blank titration wasperformed as a control.

Calculation

The volumes of KOH solution added versus the corresponding electrodepotential (mv) were plotted. The inflection points A and B for oilsample and solvent only were marked, which are believed to reflect thelargest potential changes for a unit KOH. The TAN was calculated usingthe following equation: Acid number (mg KOH/g)=(A−B)×M×56.1/W, in whichM is the concentration of alcoholic KOH solution (mol/L) and W is thesample mass (g).

Results

Two typical titration curves for KOH to KHP and KOH to oil are shown inFIG. 5A and FIG. 5B. In each case, the inflection points are clearlyobserved. The results are consistent with the data obtained from The OilAnalysis Lab, as shown in Table 1. TABLE 1 Results of TAN MeasurementTang Lab Oil Analysis Lab TAN 4.35 (1st), 4.29 (2nd) 4.35 (1st), 4.38(2nd)

EXAMPLE 2 Catalytic Decarboxylation for Naphthenic Acid Removal fromCrude Oils

This Example outlines a process useful for the catalytic decarboxylationof naphthenic acids in crude oil. MgO was shown to have decarboxylationactivity with both saturated and aromatic model naphthenic acidcompounds in a 4 hour reaction carried out at a temperature range of150° C. to 250° C. In the presence of Ag₂O, the amount of CO₂ producedmatched the amount of the other decarboxylation product, naphthalene,resulting in a “direct” catalytic decarboxylation. These findingsprovide a low-temperature, cost-effective catalytic decarboxylationprocess to remove naphthenic acids from oil. Furthermore, this Exampledemonstrates that catalytic decarboxylation reactions of naphthenicacids in the presence of various solid catalysts have been investigated.Among catalysts tested, MgO exhibits the high reactivity toward thedecarboxylation of model saturated and aromatic naphthenic acidcompounds. Ag₂O not only promotes acid conversion, but also “directly”converts naphthoic acid to naphthalene.

Experimental Methods

Selected Model Compounds and Oil Samples

A pair of carboxylic acids, naphthoic acid (C₁₀H₇COOH) and cyclohexanecarboxylic acid (CHCA) were selected as the model compounds to representthe aromatic and saturated naphthenic acids.

Five organic acids (cyclopentane carboxylic acid (CPCA), cyclohexanecarboxylic acid (CHCA), benzoic acid (BA), C₅H₁₁—CHCA and C₇H₁₅-BA) weredissolved in dodecane resulting in weight concentrations in a range of0.871%˜2.471%.

Texaco crude oil, donated by ChevronTexaco with Total Acid Number (TAN)of 4.38 was used in the study.

Experimental Setups

NA sample, catalyst, and other additive, in orders of milligram, weresealed in a glass tube under a reduced atmosphere. The sealed glasstubes were placed in oven to undergo reaction under with a controlledtemperature. The gas produced by the reaction was collected andquantified in a vacuum line via a standard gas transfer method.

For crude oil test experiments, a different experimental procedure wasestablished that used a 40 mL autoclave reactor to carry out thereaction instead a glass tube. Detailed description of the procedure isas follows: (i) 12 g oil and 0.24-0.60 g catalyst (2˜5 wt % of oil) wereloaded into the reactor; (ii) the two components were pre-mixed byshaking the reactor for one hour; (iii) the reaction was allowed to runat temperature of 250˜300° C. for 4 hours with the continuous shaking ofthe reactor to achieve a good contact between the oil and the catalyst;(iv) after the desired reaction time had elapsed, the reactor wascooled, and the treated oil was separated from the catalyst by vacuumfiltration.

Analysis Methods

The reaction gas was collected and quantified in a vacuum line via astandard gas transfer method. The resulting gas was then analyzed withGC to quantify the amount of CO₂ and other gases produced in thereaction. The solid residue, which presumably contained the unreactedacids, was extracted using dichloromethane and subjected to GC analysis.These numbers were used to calculate the amount of acid conversion thatoccurred.

For crude oil tests, the Total Acid Numbers (TAN) of the naphthenicsamples, before and after reactions, were measured by Standard TestMethod for Acid Number of Petroleum Products by PotentiometricTitration, ASTM-D 664. This work was performed at The Oil Analysis Lab.

Theoretical Methods

The gas phase geometries of reactants, products, intermediates andtransition states (TS) have been optimized using the B3LYP flavor ofdensity functional theory. The 6-31G(d) basis set for all ofcomputations were used. All stationary points have positively identifiedfor local minima (zero imaginary frequencies) and for TS (one imaginaryfrequency). Vibration frequencies were also calculated at all stationarypoints to obtain zero point energies (ZPE) and thermodynamic parameters.

Results

Catalytic Decarboxylation of Model Compounds

Table 2 lists the CO₂ generation of catalytic reactions. Among thevarious solid catalysts that were tested, the amounts of the CO₂generated from MgO for both saturated and aromatics (30.38 and 33.20ml/g, corresponding to the 17.4% and 25.5% mol conversion) were muchhigher than that from other solid catalysts. A lack of CO₂ formationdoes not necessarily mean that acid conversion did not occur, as it islikely that some of the CO₂ was adsorbed by the metal oxides to formcarbonates. However, detection of CO₂ clearly indicates the conversionof acid compounds. MgO exhibited the highest reactivity towards thedecarboxylation of the naphthenic compounds. Addition of the organicbases, such as pyridine, can slightly promoted the catalytic reactivity.In the presence of pyridine, MgO catalyzed decarboxylation occured attemperatures as low as 100° C. TABLE 2 Catalytic Decarboxylation ofModel Compounds Acid Wt. Catalyst Additive (mg) CO₂ Name (mg) Name Wt.(mg) Name wt. (mg) (ml/g) CHCA 49.3 MgO 10.2 30.38 CHCA 50.9 CaO 14.30.00 CHCA 51.9 BaO 11.5 0.02 CHCA 46.1 SrO 11.5 0.00 NA 51.5 None 0.00NA 52.8 MgO 19.7 33.20 NA 50.8 CuO 11.3 0.00 NA 52.4 Cu₂O 11.7 0.00 NA50.5 Al₂O₃ 10.1 0.00 NA 49.1 Cu₂O 9.6 C₅H₅NO 48.4 5.60 NA 52.7 MgO^(b)21.3 Pyridine 56.2 20.80Reaction temperature and time are 200° C. and 4 hrs, expect for ^(b)reaction temperature and time for 100° C. and 4 hrs.Catalytic Decarboxylation of the Acid Mixture

To test effectiveness of the developed MgO series catalyst ondecarboxylation of organic acids, a mixture of five acid compounds wasprepared to partly simulate an oil composition with an elevated acidcontent. As listed in Table 3, higher acid conversions were obtainedfrom MgO, in the case of a single acid test. The acid conversions werefurther improved when small amounts of Ni and Cu were loaded on MgO andthe conversions reached >90%. TABLE 3 Catalytic Decarboxylation of AcidMixture Catalyst Acid Conversions Mixture wt. C5H11- C7H15- wt. (g) Name(mg) CPCA CHCA BA CHCA BA 2.49 None 16.0 15.0 14.5 11.3 7.0 2.53Ni/Al₂O₃ 25.8 5.0 5.7 15.0 10.7 4.8 2.54 Ni/SiO₂ 25.5 21.5 18.9 15.416.0 8.7 2.55 Ni/MgO 25.5 70.8 70.5 91.2 92.4 97.5 2.38 Cu/Al₂O₃ 27.20.0 0.0 5.5 2.4 5.3 2.38 Cu/SiO₂ 25.0 12.8 10.5 10.4 7.1 3.5 2.50 Cu/MgO25.4 86.5 83.9 92.4 93.2 98.0 2.54 MgO 25.5 39.0 46.7 78.8 81.6 92.5CPCA, cyclopentane carboxylic acid;CHCA, cyclohexane carboxylic acid,BA, benzoic acid, 200° C., 4 hr.MgO-Catalyzed Decarboxylation Reactions

The temperature dependence and MgO loading effect of naphthenic aciddecomposition during the reaction was investigated. The reactions wererun separately by changing reaction temperatures in the range of 100 to300° C. at a fixed MgO loading, 20 wt %, and changing the MgO loadingfrom 0 to 40 wt % at 250° C. Gaseous and the remaining solid productswere analyzed to obtain the data for the CO₂ yield as well as the acidconversion.

The results as shown in FIG. 6 show that the acid conversion began ataround 150° C., increased rapidly in the range of 150-250° C., and thenleveled off at higher temperatures. At temperatures above 250° C., morethan 80% of acid was converted, while the CO₂ yield did not continue toincrease. Increasing of the MgO loading in the range of 0-20 wt %linearly increased the CO₂ yield and the acid conversion, but furtherincreases in the amount MgO loading did not further increase the CO₂yield.

Mechanistic Studies of the MgO-Catalyzed Decarboxylation Reaction

A plausible concerted oxidative decarboxylation pathway in the presenceof MgO has been theoretically studied in gas-phase with the energydiagram of all of stable, intermediated and transition states computed.The reaction path is summarized as a three-step mechanism that convertsbenzoic acid to phenol, as shown in FIG. 7:

-   -   Step 1: Nucleophilic attack at the C atom of the carboxyl group,        from (A) to (B);    -   Step 2: Transfer of the hydroxy group via a 4-member ring        transition state, from (B) to (D) through TS-1 (C);    -   Step 3: Proton transfer accomplishing by decarboxylation,        from (D) to (F) through TS-2 (E).

The computed transition barrier for TS-1, featuring attacking of thehydroxy group on the ortho-position of the aromatic ring (˜30 kcal/mol)is consistent with experimental conditions (200° C., 4 hrs) disclosedherein. The barrier for TS-2, featuring proton transferring from ortho-to ipso- (49 kcal/mol), however, is higher than expected. This could bepartially due to the fact that only gas-phase, single-moleculecalculations were performed. Further calculations with larger metaloxide clusters, and/or water assisting are expected to lower thisbarrier.

The CO₂ Yield vs. the Acid Conversion

While most of the metal oxides tested did result in CO₂ production, acidconversion may still have occurred. In fact, by comparing the CO₂ yieldand the acid conversion in the presence of several metal oxides, asshown in Table 4, is becomes clear that the acid conversion is ingeneral much higher than the CO₂ yield in most cases. This largedifference could be either due to the formation of carboxylic acid saltsthrough a traditional acid-base reaction, or the formation of alkalineearth metal carbonates through the adsorption of CO₂ by metal oxides.These formations are, however, known to lead to series emulationproblems that make them less appealing. In this sense, the case of Ag₂Ois certainly a good choice of “clean” catalyst, because the acidconversion agrees with the CO₂ yield. Furthermore, the decarboxylatedproduct, naphthalene, was also detected. This clearly indicates that a“direct” catalytic decarboxylation reaction did occur. TABLE 4Comparison of the CO₂ Yield and the Acid Conversion in the Presence ofSeveral Metal Oxides Acid Conversion CO₂ Yield Catalyst (%) (%) None 3.60.05 MgO 81.6 17.1 CaO 96.9 0 SrO 69.9 0 BaO 53.8 0.15 Ag2O 53.7 53.1CuO 17.2 63.3250° C.; cat ˜10 mgTest Runs with Crude Oil

The results of initial test runs of a group of metal oxide catalysts asreagents towards the decarboxylation reaction of crude oils areillustrated in FIG. 8. CaO shows a high acid conversion, ˜70%, whileMgO, Ag₂O, and CuO did not show significant reactivity towards the acidremoval as expected, likely due to deactivation of the catalystresulting from impurities in the oil.

EXAMPLE 3 Catalytic Decarboxylation of Naphthoic Acid Using Rare EarthMetal Oxides

Several rare earth metal oxides, including CeO₂, La₂O₃, Y₂O₃ and ZrO₂were tested with model acid, naphthoic acid (C₁₀H₇COOH) and the resultwas shown in Table 2. The low CO₂ yields, defined as the carbonconversion to CO₂ as shown in Table 5, suggest that they were inactivetowards catalytic decarboxylation. The metal oxide ZrO₂ exhibitedacid-base dual functionalities. TABLE 5 Catalytic Decarboxylation ofNaphthoic Acid in the Presence of Rare Earth Metal Oxides Temp Run #Acid (mg) Catalyst (mg) (° C.) RT (hr) CO₂ yield (%) 151 NA 51.6 152 NA47.7 CeO₂ 10.6 250 4 0.16 152 NA 49.7 La₂O₃ 10.4 250 4 0.01 154 NA 50.6Y₂O₃ 10.5 250 4 0.00 155 NA 51.2 ZrO₂ 11.1 250 4 0.00 177 NA 51.6 ZrO₂13.3 300 4 0.94NA, C₁₀H₇COOH, 2-naphthoic acid

EXAMPLE 4 Catalytic Decarboxylation of Naphthenic Acids Using OxidativeTransition Metal Oxides

More oxidative metal oxides were investigated in the catalyticdecarboxylation of model compounds, naphthoic acid and cyclohexanepentanoic acid. The latter is considered to be more representative asthe component of naphthenic acid in crude oil. The tested metal oxidesinclude Ag₂O, AgO, MnO₂, Mn₂O₃, PbO₂, CuO, Cu₂O, Fe₂O₃ and CO₂O₃. All ofthese metal oxides have variable oxidative states.

The data in Table 6 show that the CO₂ formation, which is an indicationof the catalytic decarboxylation, was detected in each case except forFe₂O₃. At the temperature of 250° C., the CO₂ yields were all lower than10% although the acid conversion could reach higher. Increasing thereaction temperature to 300° C. resulted in the higher CO₂ yields, aswell as higher acid conversions, suggesting that the catalyticactivities of these metal oxides are temperature sensitive. Importantly,the CO₂ yield from Ag₂O reached as high as 96.93%, indicating thenaphthoic acid has been almost completely converted to CO₂. The highacid conversion of 93.3% is consistent with these data. In addition,naphthalene, as another important decarboxylated product, was alsodetected. The yield of naphthalene, defined as the carbon conversion tonaphthalene, reached 66.2%. Moreover, The GC-MS analysis also identifiedthe formation of 1,2′-binaphthalene and 2,2′-binaphthalene (C₂₀H₁₄).These byproducts might be the result of dimerization of naphthalene.This result strongly suggested that the reaction occurred through aradical mechanism.

Comparison of the same metal atoms at different oxidative states doesnot show a general trend on their decarboxylation efficiency. Forinstance, Ag(I) is much more active than Ag(II), but Mn(IV) yields moreCO₂ than Mn(III), while Cu(I) and Cu(II) gave almost equal CO₂ yields atthe temperature of 300° C.

When applying Ag₂O, MnO₂ and PbO₂ to a new acid substrate, cyclohexanepentanoic acid (CHPA), CO₂ was also detected although the yields werenot as high due to the lower reaction temperature. These results showpromise for the application of oxidative metal oxide catalysts to reactwith diverse acid substrate structures.

Regarding the mechanism of catalytic decarboxylation on oxidative metaloxides, oxidative decarboxylation via radical intermediate would be themost plausible reaction path. Accordingly, the oxidative abilities ofthese compounds will be essential to the activities. TABLE 6 CatalyticDecarboxylation of Model Carboxylic Acids in the Presence of OxidativeMetal Oxides Acid (mg) Catalyst (mg) Temp (° C.) RT (hr) Acid conv (%)CO₂ yield (%) C₁₀H₈ Yield (%) C₂₀H₁₄ NA 60.0 Ag₂O 9.8 250 4 26.0 3.6 NA49.7 MnO₂ 10.0 250 4 34.2 3.3 NA 56.6 Mn₂O₃ 10.2 250 4 20.2 2.8 NA 50.2PbO₂ 11.8 250 4 24.9 4.5 NA 49.9 CuO 10.2 250 4 53.9 3.5 NA 57.6 Cu₂O10.7 250 4 59.2 6.7 NA 49.5 Fe₂O₃ 9.7 250 4 40.2 0.0 NA 55.2 Co₂O₃ 10.7250 4 16.0 6.0 NA 54.0 Ag₂O 10.8 300 4 93.9 96.9 66.2 detected NA 48.3AgO 10.2 300 4 16.1 15.4 2.2 NA 49.7 MnO₂ 11.5 300 4 74.3 17.1 0.5detected NA 52.6 Mn₂O₃ 10.7 300 4 61.8 5.2 NA 49.9 PbO₂ 10.8 300 4 38.45.2 NA 52.2 CuO 11.5 300 4 56.5 20.9 4.4 NA 50.2 Cu₂O 10.1 300 4 63.622.9 13.7 CHPA 64.0 Ag₂O 9.4 250 4 10.6 2.8 CHPA 65.6 MnO₂ 10.3 250 436.2 5.5 CHPA 72.2 PbO₂ 13.9 250 4 24.4 5.3NA, C₁₀H₇COOH, 2-naphthoic acidCHPA, C₆H₁₁C₄H₈COOH, Cyclohexane pentanoic acid

EXAMPLE 5 Kinetic Measurement with Crude Oil in the Presence of SolidCatalysts

The TAN, oil viscosity and IR adsorption of the treated oil weremeasured at different reaction stages using multiple cold traps. Twocatalysts, MgO and MnO₂, were investigated. MgO and MnO₂ have been shownto be effective to the decarboxylation of model compounds and theremoval of naphthenic acid from crude oil in batch reaction tests.

In the reaction, 0.5 g of catalyst (particle size 28-65) and crude oilfrom Texaco with 2% CHPA added were added to a reactor at a flow rate of3-4 g/hr. During the reaction, infrared spectroscopy (IR) was used tomonitor the effectiveness of the catalyst. The catalyst was consideredto be deactivated if the RCOOH absorption (as indicated by a peak ataround 1,700 nm) significantly recovered. When this occurred, thereaction was complete. The oils were collected at different reactionintervals and were subjected to TAN analysis and viscosity measurement.

The thermal treatment results at different temperatures are shown inFIG. 9 and Table 7. IR measurement showed that the temperature effectexhibits an increase followed by decrease. The TANs for the oils treatedat 250° C. and 300° C. were found to be higher than the starting feed.This may have been due to the evaporation of some light components otherthan naphthenic acid in this temperature range, resulting in an apparentincrease in the naphthenic acid concentration. If the temperature wasincreased further to around 350° C., some naphthenic acids may haveevaporated or decomposed, leading to the lower acidity.

For MgO catalyst, the reaction was continuously run for 29.25 hr intotal (80° C. for 2 hr, 150° C. for 2 hr, 250° C. for 21.33 hr, and 300°C. for 4 hr) with the result shown in FIG. 6 and Table 8. The IRmeasurement showed that the catalyst was effective until 9 hr at 250° C.(13 hr total). At this time, 47.74 g of oil was collected was and theoil treatment capacity was calculated to be 95.48 g-oil/g—MgO. The TANof the oil decreased more than 30% after 13 hr in stream.

The inventors further increased the reaction temperature to 300° C. andthe oil was treated with MgO catalyst for a longer time, as illustratedin FIG. 10 and Table 9. IR measurement showed that the deactivationstarted from 12 hrs, 30 min. The TAN measurement gave lower values of5.6 and 7.9 for the oils collected during the reaction time 2-4 and 5-8hrs periods, respectively. The acid conversion calculated based on TANdecrease have reached to 64-50%. By continuously increasing the reactiontemperature to 350° C., the collected oil flowed more readily. This ledto the lower viscosity. While not wishing to be bound to any particulartheory, it is believed that catalytic cracking, perhaps promoted by MgO,may have led to this result.

On the role of MgO to acid removal, it is considered have multiplemechanisms. The results with model acid compound identified itsdecarboxylation activity, due to the CO₂ formation. Meanwhile, becauseof its inherent strong basicity, MgO will also tend to react with acidthrough acid-base neutralizsation. At higher temperature, MgO isreported to be active to promote C—C cracking of hydrocarbons.

The inventors ran a flow test on MnO₂, as illustrated in FIG. 12 andTable 10. For MnO₂ catalyst, the reaction was continuously run at 250°C. for 10 hr, 30 min. The IR measurement showed that MnO₂ was effectiveto RCOOH reduction at the early reaction stage and then the peaksincreased gradually with the reaction time. After 10 hr, 35 min, it wasrecovered almost completely. The TAN analysis showed that TAN of the oildecreased to some degree until 4.17 hr and the oil treatment capacitywas around 51 g oil/g—MnO₂. TABLE 7 TAN and Viscosity Measurement forthe Thermal Treated Viscosity (40° C./ Temp (° C.) TAN 70° C.) 80 11.53060/239 150 11.1 4850/428 250 14.5 3720/368 300 15.8 3050/256 350 10.36203/496

TABLE 8 TAN and Viscosity Measurement for the Oil Treated with MgO below250° C. Bottle Oil Collecting Elapsed Temp Viscosity Conv. No time (hr)time (hr) (° C.) TAN (40° C.) (%) 0 14.1 4640 1 1.92 1.92 80 10.2 2 2.003.92 150 10.3 3 4.08 8.00 250 11.3 9120 22.1 4 5.00 13.00 250 9.3 35.9 55.25 18.25 250 12.8 7500 6 5.17 23.42 250 10.1 7 1.83 25.25 250 17.1 84.00 29.25 300 10.4 3280MgO, 0.5 mg

TABLE 9 TAN and Viscosity Measurement for Oil Treated with MgO at 300°C. and 350° C. Bottle No. Temp (° C.) Time Period (hr) Oil collected (g)Flow rate (g/hr) IR_(RCOO) TAN Viscosity (40/70° C.) Conv % Bottle 1<300° C.   5.30 weak 10.5 33.1 Bottle 2 300° C. 0-1 hr 5.56 5.56 weak8.8 44.4 Bottle 3 300° C. 2-4 hr 6.17 2.06 weak 5.6 64.3 Bottle 4 300°C. 5-8 hr 12.92 3.23 weak 7.9 12700/1040  49.8 Bottle 5 300° C. 9-12.515.26 3.39 weak 16.9 10320/630  −7.5 Bottle 6 300° C. 12.5-20.67 hr27.38 3.35 strong 9.1 5020/376  42.2 Bottle 7 300° C. 20.67-25 hr 16.343.70 strong 12.5 3310/318  20.7 Bottle 8 350° C. 1-5 hr 15.70 3.14unstable 13.7 835/107 Bottle 9 350° C. 6-7 hr 4.70 2.35 unstable 12.3Bottle 10 N₂ purge 2.96 weak 4.1MgO 0.5 g, 300° C., 350° C.Feed, Oil + 2% CHPA

TABLE 10 TAN and Viscosity Measurement for the Oil Treated with MnO₂ at250° C. Flow reaction-7, MnO₂, 0.50 g Elapsed time (hr) Temp (° C.) TAN0 RT 14.13 0.50 <250 11.15   0-1.17 hr 1.17 250 11.04 1.17-2.17 hr 2.17250 12.42 2.17-4.17 hr 4.17 250 11.89 4.17-9.92 hr 9.92 250 15.27 >9.92hr, N2 purge 10.30 250 9.76Flow rate: 4.57˜2.08 ml/hr

EXAMPLE 6 Adsorption of Naphthenic Acids onto Clay Minerals

Model naphthenic acid (NA) solutions were prepared by using fourcommercial NAs (i.e., cyclohexanepropionic acid (NA1), benzoic acid(NA2), cyclohexanepentanoic acid (NA3), and 4-heptylbenzoic acid (NA4))with tetradecane dissolved in dodecane (C12). Their concentrations wereabout 0.5% each in weight percent. Several clay samples (from the SourceClay Repository of Clay Mineral Society at Purdue University, WestLafayette, Ind.), ie., kaolin (KGa-2), illite (IMt-1), illite-smectitemixed layer 60/40 (ISMt-2), illite-smectite mixed layer 70/30 (ISCz-1),palygorskite (PF1-1), montmorillonite (SAz-1), Ca-montmorillonite(SAz-2), montmorillonite, CA (SCa-3), sepiolite (SepSp-1), hectorite(SHCa-1), and Na-montmorillonite, WY (SWy-2), were chosen as modelabsorbents for this study. The chemical compositions of clay mineralsused are shown in Table 11.

The adsorption experiments were carried out using the batchequilibration technique. Desired amounts of a NAs solution were added todifferent glass centrifuge tubes, which contained known amounts of clayminerals. The tubes were shaken at 25° C. and 66° C. for 24 hours,followed by centrifugation for 10 min. Supernatants were sampled andsubject to analysis to determine the NA concentration using a HewlettPackard Gas Chromatography-Mass Spectroscopy (GC-MS). No changes insolute concentrations without clays were detected in the tubes withinthe experimental period. Therefore, solute mass lost in the supernatantfrom clay slurries was assumed to be adsorbed by clay. The amount of NAsadsorbed was calculated from the difference between the initial andequilibrium solute concentration in dodecane solution. TABLE 11 ChemicalComposition of Clay Minerals Cation exchange Surface Clay Chemicalcomposition (%) capacity area code Description SiO₂ Al₂O₃ TiO₂ Fe₂O₃ FeOMnO MgO CaO Na₂O K₂O (meq/100 g) (m²/g) KGa-2 Kaolinite, high defect43.9 38.5 2.08 0.98 0.15 n.d. 0.03 n.d. <0.005 0.065 3.3 23.5 IMt-1Illite 49.3 24.25 0.55 7.32 0.55 0.03 2.56 0.43 0 7.83 n/a n/a ISCz-1Illite-Smectite, 70/30 51.6 25.6 0.039 1.11 <0.1 0.04 2.46 0.67 0.325.36 n/a n/a ISMt-2 Illite-Smectite, 60/40 51.2 26.3 0.17 1.49 0.1 0.012.41 1.4 0.04 4.74 n/a n/a PF1-1 Palygorskite 60.9 10.4 0.49 2.98 0.40.058 10.2 1.98 0.058 0.8 19.5 136.35 SAz-1 Montmorillonite (AZ) 60.417.6 0.24 1.42 0.08 0.099 6.46 2.82 0.063 0.19 120 97.42 SAz-2Ca-Montmorillonite 60.4 17.6 0.24 1.42 0.08 0.099 6.46 2.82 0.063 0.19120 97.42 (AZ) SCa-3 Montmorillonite (CA) 52.8 15.7 0.181 1.06 <0.100.03 7.98 0.95 0.92 0.03 n/a n/a SepSp-1 Sepiolite 52.9 2.56 <0.001 1.220.3 0.13 23.6 <0.01 <0.01 0.05 n/a n/a SHCa-1 Hectorite 34.7 0.69 0.0380.02 0.25 0.008 15.3 23.4 1.26 0.13 43.9 63.19 SWy-2 Na-Montmorillonite62.9 19.6 0.09 3.35 0.32 0.006 3.05 1.68 1.53 0.53 76.4 31.82 (WY)

Table 12 summarizes the results of NAs adsorbed onto the selected clayabsorbents. The order of the affinity of various clays as adsorbents toNAs is:SepSp-1>SWy-2>SAz-1>PF1-1>SHCa-1≧SCa-3>SAz-2>IMt-1>IScz-1>KGa-2>ISMt-2.In addition, in each test no significant adsorption was observed fortetradecane. This result shows that these clay adsorbents are selectivetoward NAs but not hydrocarbon. This demonstrates that sepiolite(SepSp-1) and Na-montmorillonite (SWy-2) are potential efficientadsorbents for removing NAs from crude oil. The capacity of theadsorption of NAs reached 68 and 53 mg-acid/g-clay for SepSp-1 andSWy-2, respectively. In contrast, ISCz-1 was found to be inactivetowards the acid adsorption. In most of clays used, the order of theaffinity of four NAs adsorbed onto clays is: NA2>NA3>NA1>NA4, exceptonto KGa-2. The adsorption of benzoic acid onto the clays was moreeffective in comparison with the adsorption of other NAs. Benzoic acidwith an aromatic ring showed strong effect on physical-chemicaladsorption.

The analysis of the minerals is reported as percentages of oxide, ratherthan as percentages of metals as shown in Table 11. The NA adsorptionwas correlated with the concentrations of MgO, CaO, and Na₂O,individually or together. The amount of NAs adsorbed was found toroughly increase with the amount of MgO (FIG. 13). The adsorption of theNAs may be affected by the chemical structures of clay. TABLE 12Efficiency of Acid Removal from the Selected Clay Absorbents NAsAdsorbed Percentage (%) Amount of NAs Adsorbed Adsorbent NA1 NA2 NA3 NA4(mg/g) KGa-2 5.5 6.6 11.1 1.9 9.7 IMt-1 15.7 24.5 19.1 8.1 25.7 ISCz-11.6 25.7 3.1 3.6 12.2 ISMt-2 0.0 0.0 0.0 0.0 0.0 PF1-1 20.1 34.3 20.226.9 38.9 SAz-1 21.2 46.7 23.7 13.5 40.0 SAz-2 15.4 30.8 22.3 8.5 29.3SCa-3 16.1 30.6 19.4 8.7 34.1 SepSp-1 37.9 60.0 39.2 40.9 68.0 SHCa-117.4 40.4 19.4 11.8 33.9 SWy-2 17.7 47.0 23.3 49.8 53.0NA1 = Cyclohexanepropionic acid, FW = 156.23NA2 = Benzoic acid, FW = 122.1NA3 = Cyclohexanepentanoic acid, FW = 184.28NA4 = 4-Heptylbenzoic acid, FW = 220.31

EXAMPLE 7 Reduction of TAN and Viscosity of in Crude Oil FollowingCatalysis by MgO

1 g MgO with a particle size of 20-60 mesh was added to a sample ofcrude oil in a flow reactor. Reactions were carried out at 300° C. and350° C. The reaction run at 300° C. was run for 54 hr, and during thereaction, the flow rate of the oil changed from 15.35 to 1.76 mL/hr,mostly in the range of 2-5 mL/hr. The total oil collected during thereaction was 206.23 g. The TAN changes at the different reaction stagesare plotted in FIG. 14. The TAN of the starting oil was 4.79, and theTAN of the treated oil was in the range of 2.42 to 3.20. The catalystremained active more than 48 hr, and the TAN reduction rates were in therange of 33.2 to 49.9%. The results of the experiment at 300° C. areshown in Table 13. TABLE 13 Flow reaction of crude oil with MgO at 300°C. Time (hr) TAN TAN reduction (%) Viscosity/40° C. 0 4.79 6300 1 2.4249.5 5 2.96 38.2 1-5 8640 11 3.20 33.2 19 3.03 36.7 24 3100 26 3.01 37.235 2.40 49.9 48 2.94 38.6 6380MgO 1.0 g, 20-60 mesh

For the reaction sample that was tested at 350° C. for 7.7 hr, the TANdecreased from 4.72 to 1.75, and the viscosity decreased from 6,300 cPto 174 cP at 40° C. The estimated API for the treated oil was 18degrees, and the original feed (crude oil) was around 13 degrees.

A similar reaction was carried out at 325° C. for 8 hr. In this case,the TAN decreased from 4.72 to 2.91, and the viscosity at the end wasroughly half of what it was at the beginning.

EXAMPLE 8 Reaction of Mixed Acid in the Presence of Catalysts

Acid conversion analyses were performed using MgO in the presence ofnickel and Al₂O_(3.) A mixed acid solution comprising the followingacids was used: CPCA (cyclopentane carboxylic acid) 2.47%; CHCA(cyclohexane carboxylic acid) 1.93%; BA (benzoic acid) 0.87%; C5H11-CHCA1010%; C7H15-BA 1.11%. The solvent used for the reaction was decane. Thereaction was carried out at 200° C. for 4 hours. The results are shownbelow in Table 14. TABLE 14 Reaction of Mixed Acid in the Presence ofCatalysts Catalyst (Ni 0.5 wt %) None MgO Ni/MgO Ni/Al₂O₃ Catalystloaded (mg) 25.5 25.5 25.8 Mixed acid solution* amount (g) 2.49 2.542.55 2.53 Conversion of acid (%) CPCA 16.0 39.0 70.8 5.0 CHCA 15.0 46.770.5 5.7 BA 14.5 78/8 91.2 15.0 C₅H₁₁-CHCA 11.3 81.6 92.4 10.7 C₇H₁₅-BA7.0 92.5 97.5 4.8

EXAMPLE 9 Improved Oil Upgrading Using a Catalyst with Higher MechanicalStrength and Catalyst With Added Inert Materials

In flow reaction 20 (FR20), the reaction was run continuously for 164hours with 1.0 g MgO at 325° C. with a flow rate of 2.05 to 6.56 mL/hr.In this reaction, glass beads were added to the catalyst to suppressmovement of catalyst particles. In addition, the MgO used had a meshsize of 40-60. The TANs for the treated oil in this reaction werereduced by about 20-30%. The results of FR20 are shown in Table 15.TABLE 15 Results of Flow Reaction 20 Table 2 Flow run # 20 Texaco crudeoil     Catalyst: MgO, 40-60 mesh, 1.0 g   Temperature: 325° C. Totaloil collected Flow rate Bottle No. Run hour Total run hrs Oil collected(g) (g) (ml/hr) TAN Red % 1 1.00 5.92 5.92 5.92 2 1.50 1.50 14.17 20.099.45 22.1 3 3.17 4.67 14.61 34.70 4.61 4 4.83 9.50 13.6 48.30 2.82 25.75 6.75 16.25 19.45 67.75 2.88 6 5.42 21.67 24.13 91.88 4.45 24.7 7 5.0026.67 21.44 113.32 4.29 8 6.83 33.50 19.04 132.36 2.79 9 7.75 41.2519.46 151.82 2.51 10 4.25 45.50 27.86 179.68 6.56 11 7.00 52.50 28.26207.94 4.04 18.8 12 2.00 54.50 4.09 212.03 2.05 13 25.00 79.50 86.03298.06 3.44 23.5 14 24.00 103.50 86.16 384.22 3.59 28.5 15 20.67 124.1773.31 457.53 3.55 16 23.83 148.00 79.64 537.17 3.34 17 16.00 164.0050.96 588.13 3.19

In an additional reaction, (FR21), the temperature was raised to 350°C., and the flow rate was set to 1.0 mL/hr, and the reaction was run for40.9 hrs. In this case, the TAN decreased from 4.71 to 1.74, and theviscosity decreased from 6,300 to 282 cP (at 40° C.). The API of theresulting oil is estimated to be 17.7 degrees. The results of FR20 areshown in Table 16. TABLE 16 Results of Flow Reaction Table 3 Flow run #21 Texaco crude oil, TAN 4.71, API 13.2   Catalyst: MgO, 40-60 mesh, 2.0g   Temperature: 350° C. Oil collected Total oil Flow rate Viscosity, cpAPI Bottle No. Run hour Total run hrs (g) collected (g) (ml/hr) TAN (40°C.) Gravity 1 0.42 0.42 5.73 5.73 13.64 2 2.25 2.25 17.78 23.51 7.902.45 3 9.33 11.58 16.98 40.49 1.82 1.98 605 16.6 4 29.33 40.91 20.0460.53 0.68 1.74 282 17.7 5 19.67 60.58 22.28 82.81 1.13 420 17.1 6 8.8369.41 14.11 96.92 1.60 600 16.5 7 20.17 89.58 20.70 117.62 1.03

1. A method for upgrading oil, comprising contacting a quantity of anoil with an amount of a metal oxide agent sufficient to upgrade thequantity of oil.
 2. The method of claim 1, wherein the metal oxide agentis selected from the group consisting of alkaline earth metal oxides,oxidative transition metal oxides, rare earth metal oxides, andcombinations thereof.
 3. The method of claim 2, wherein the alkalineearth metal oxide is selected from the group consisting of oxides ofberyllium (Be), oxides of magnesium (Mg), oxides of calcium (Ca), oxidesof strontium (Sr), oxides of barium (Ba), and combinations thereof. 4.The method of claim 3, wherein the alkaline earth metal oxide isselected from the group consisting of calcium oxide (CaO), magnesiumoxide (MgO), and combinations thereof.
 5. The method of claim 2, whereinthe oxidative transition metal oxide is selected from the groupconsisting of oxides of silver (Ag), oxides of copper (Cu), oxides ofmanganese (Mn), oxides of lead (Pb), oxides of nickel (Ni), andcombinations thereof.
 6. The method of claim 5, wherein the oxidativetransition metal oxide is selected from the group consisting of AgO,Ag₂O, and combinations thereof.
 7. The method of claim 2, wherein therare earth metal oxide is selected from the group consisting of oxidesof cerium (Ce), oxides of lanthanum (La), oxides of yttrium (Y), oxidesof zirconium (Zr), and combinations thereof.
 8. The method of claim 1,wherein contacting is performed within a temperature range selected fromthe group consisting of from about 200° C. to about 450° C., from about250° C. to about 450° C., from about 300° C. to about 450° C., fromabout 350° C. to about 450° C., and from about 400° C. to about 450° C.9. The method of claim 1, wherein contacting is performed within atemperature range of from about 300° C. to about 370° C.
 10. The methodof claim 1, wherein contacting is carried out in a reaction systemselected from the group consisting of a sealed glass tube, an autoclave,a flow reactor, a batch reactor, a slurry reactor, and combinationsthereof.
 11. The method of claim 1, wherein the quantity of oil islocated in a subsurface reservoir.
 12. The method of claim 1, whereinthe oil is a fat-based oil.
 13. The method of claim 1, furthercomprising adding a quantity of water to dissolve water-solubleimpurities.
 14. The method of claim 1, further comprising adding aquantity of pyridine to promote acid conversion.
 15. The method of claim1, further comprising adding a quantity of nickel (Ni) to promote acidconversion.
 16. The method of claim 1, further comprising adding aquantity of copper (Cu) to promote acid conversion.
 17. The method ofclaim 1, further comprising adding a quantity of Al₂O₃ to promote acidconversion.
 18. The method of claim 1, further comprising contacting thequantity of oil with an amount of an adsorbent material sufficient toreduce the total acidity of the quantity of oil.
 19. The method of claim18, wherein the adsorbent material is a clay mineral or a mixture ofclay minerals.
 20. The method of claim 18, wherein the clay mineral isselected from the group consisting of kaolinite, illite,illite-smectite, palygorskite, montmorillonite, Ca-montmorillonite,sepiolite, hectorite, Na-montmorillonite, and combinations thereof. 21.The method of claim 18, wherein contacting the quantity of oil with theamount of the metal oxide agent and contacting the quantity of oil withthe adsorbent material occur in parallel, in series, or simultaneously.22. The method of claim 18, wherein the adsorbent material catalyzesacid conversion.
 23. A method for reducing the total acidity of aquantity of oil, comprising contacting the quantity of oil with anamount of a metal oxide agent sufficient to reduce the total acidity ofthe quantity of oil.
 24. The method of claim 23, further comprisingreducing the total acid number of the oil.
 25. The method of claim 23,further comprising reducing a quantity of naphthenic acids in saidquantity of oil.
 26. A method of reducing the viscosity of a quantity ofoil, comprising contacting the quantity of oil with an amount of a metaloxide agent sufficient to reduce the viscosity of the quantity of oil.27. The method of claim 26, further comprising increasing the APIgravity of the quantity of oil.
 28. A composition comprising a quantityof an upgraded oil, produced by a process, comprising: providing aquantity of an oil; and contacting the quantity of oil with an amount ofa metal oxide agent sufficient to upgrade the quantity of oil, wherebythe quantity of upgraded oil is produced.
 29. The composition of claim28, wherein the metal oxide agent is selected from the group consistingof alkaline earth metal oxides, oxidative transition metal oxides, rareearth metal oxides, and combinations thereof.
 30. The composition ofclaim 28, wherein the process further comprises contacting the quantityof oil or the quantity of upgraded oil with an amount of an adsorbentmaterial sufficient to reduce the total acidity of the quantity of oilor the quantity of upgraded oil.